METHOD FOR FORMING AND CONTROLLING MOLECULAR LEVEL SiO2 INTERFACE LAYER

ABSTRACT

The present disclosure provides a method for forming and controlling a molecular level SiO 2  interface layer, mainly comprising: cleansing before growing the SiO 2  interface layer, growing the molecular level ultra-thin SiO 2  interface layer; and controlling reaction between high-K gate dielectric and the SiO 2  interface layer to further reduce the SiO 2  interface layer. The present disclosure can strictly prevent invasion of oxygen during process integration. The present disclosure can obtain a good-quality high-K dielectric film having a small EOT. The manufacturing process is simple and easy to integrate. It is also compatible with planar CMOS process, and can satisfy requirement of high-performance nanometer level CMOS metal gate/high-K device of 45 nm node and below.

This application is a National Phase application of, and claims priority to, PCT Application No. PCT/CN2012/071703, filed on Feb. 28, 2012, entitled “METHOD FOR FORMING AND CONTROLLING MOLECULAR LEVEL INTERFACE SiO₂ LAYER”, which claimed priority to Chinese Application No. 201110375162.X, filed on Nov. 23, 2011. Both the PCT Application and Chinese Application are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to the field of semiconductor technology, and in particular, to a method for manufacturing a metal gate/high-K (dielectric constant) dielectric layer/SiO₂ interface layer stack structure having an ultra-thin equivalent oxide thickness (EOT) for a CMOS device. The present disclosure mainly focuses on a method for forming a molecular level SiO₂ interface layer and a control method during device manufacture. The present disclosure is applicable to manufacture of high-performance nanometer level complementary metal oxide semiconductor (CMOS) devices of 45 nm node and below.

BACKGROUND

As feature sizes of CMOS devices decrease to 45 nm and below, in order to substantially reduce gate tunneling current and gate resistance, eliminate polysilicon depletion effect, improve device reliability, and mitigate Fermi energy level pinning effect, it has become a consensus of the industry to replace conventional poly-Si (polysilicon)/SiO₂ gate structure with metal gate/high-K dielectric layer/SiO₂ interface layer gate structure. However, there are still many problems of the metal gate/high-K gate dielectric layer/SiO₂ interface layer structure waiting to be solved. For example, the problems include thermal stability problem and interface state problem, and it is difficult to obtain a small EOT and a low threshold voltage. It is desirable to obtain a good-quality high-K gate dielectric film with a small EOT. Besides a proper high K value of the high-K gate dielectric material, interfacial engineering, i.e., formation of an ultra-thin SiO₂ interface layer is also very important. Otherwise it is difficult to reduce the EOT, because the K value of the SiO₂ interface layer is low and thus has a great influence on device performances. However; it is difficult to form the ultra-thin SiO₂ interface layer, because a natural oxide layer typically has a thickness of about 5-6 Å, and the SiO₂ interface layer may continue to grow during device manufacture.

SUMMARY

The present disclosure provides a method for forming and controlling a molecular level SiO₂ interface layer for a CMOS metal gate/high-K dielectric layer device, in order to at least solve the problem of reducing the EOT.

The method for forming and controlling the molecular level SiO₂ interface layer for the CMOS metal gate/high-K dielectric layer device provided by the present disclosure comprises:

1) cleansing: after completing local oxide isolation or shallow trench isolation in Gate-First process or removing replaced gate in Gate-Last process and before forming an interface oxide layer, cleansing a wafer and immersing the wafer in HF/isopropyl alcohol/water solution at room temperature, rinsing the wafer with deionized water, spinning the wafer and then putting the wafer into a furnace immediately, wherein a volume ratio of HF:isopropyl alcohol:water is 0.15-1.5%:0.01-0.10%:1%; 2) forming the SiO₂ interface layer: performing rapid thermal annealing on the wafer in N₂ for 30-90 seconds at 500-600° C. in the Gate-Last process or at 600-800° C. in the Gate-First process; 3) forming a high-K gate dielectric film: forming the high-K gate dielectric film by physical vapor deposition or atom layer deposition, the high-K gate dielectric film may comprise one of various high-K gate dielectric films; 4) performing rapid thermal annealing: the rapid thermal annealing is conducted at 500-600° C. for 30-90 seconds in the Gate-Last process or at 800-1000° C. for 20-40 seconds in the Gate-First process; 5) forming the metal gate: depositing a metal nitride gate on the high-K dielectric layer by reactive magnetic sputtering utilizing physical vapor deposition; 6) depositing a barrier layer on the metal gate by reactive magnetic sputtering; 7) on the barrier layer, depositing polysilicon by low-pressure chemical vapor deposition in the Gate-First process and depositing low-resistance metal by magnetic sputtering in the gate-Last process; 8) etching a product of the step 7) by plasma etching with Cl-base gas, F-base gas, or a mixture thereof, using a mask having a gate photolithography pattern, to form a polysilicon/metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure or a metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure, respectively; 9) depositing silicon nitride on a product of the step 8) by plasma chemical vapor deposition at 300-400° C., the silicon nitride having a thickness of 200-600 Å; 10) etching the silicon nitride by anisotropic plasma etching to form a silicon nitride spacer-1; 11) for the Gate-First process, after source/drain extension implantation and forming a spacer-2, performing source/drain implantation to form source/drain regions; 12) for the Gate-First process, activating the source/drain regions by rapid thermal annealing: the rapid thermal annealing is performed at 950-1050° C. in N₂ for 1-15 seconds; and 13) forming contacts and metalizing: performing alloying annealing in N₂ or N₂+10% H₂ in an alloying furnace at 380-450° C.

Optionally, the cleansing in the step 1) is performed before formation of the interface oxide layer. The wafer is first cleansed by a conventional method and then is immersed in the HF/isopropyl alcohol/water solution at the room temperature for 1-8 minutes.

Optionally, in the step 2), the SiO₂ interface layer has a thickness of 0.5-0.7 nm.

Optionally, in the step 3), the high-K gate dielectric film has a thickness of 2-5 nm.

Optionally, in the step 3), the high-K gate dielectric film is one of a HfLaON film, a HfSiON film, and a HfSiAlON film.

Optionally, in the step 5), the metal nitride gate has a thickness of 3-40 nm, and the metal nitride gate is one of a TiN gate, a TaN gate, a MoN gate, a MoAlN gate, a TiAlN gate, and a TiGaN gate.

Optionally, in the step 6), the barrier layer has a Thickness of 4-7 nm, and the barrier layer is a TaN layer or an AlN layer.

Optionally, in the step 7), the polysilicon film has a thickness of 50-120 nm, the low-resistance metal film has a thickness of 50-120 nm, and the low-resistance metal film is one of a Mo film, a W film, and a TiAl film.

The present disclosure is applicable to a metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure having an ultra-thin equivalent oxide thickness (EOT) of a CMOS device. The present disclosure mainly focuses on a method for forming a molecular level SiO₂ interface layer and a control method during device manufacture. The present disclosure can achieve a good-quality high-K gate dielectric film having a small EOT and satisfy requirements of high-performance nanometer level CMOS devices of 45 nm and below.

The method for forming and controlling interfacial engineering-ultra-thin SiO₂ interface layer comprise at least four inventive steps:

1) Cleansing before growth of the SiO₂ interface layer. The present disclosure utilizes cleansing solution comprising IPA and a small quantity of HF. In this way, dangling bands on silicon surface are saturated and passivated by H+, and generation of natural oxide and contamination of particles can be suppressed. Interface micro-roughness is also improved. 2) Proposing and implementing ultra-thin SiO₂ interface layer growth technology. The ultra-thin SiO₂ interface layer is generated utilizing a trace of oxygen contained in super pure N₂ during rapid thermal annealing. The technology has a good repeatability and is a key technology in achieving the good-quality high-K gate dielectric film having the small EOT. 3) Rapid thermal annealing in super pure N₂ after the high-K dielectric is sputtered by RF reactive magnetic sputtering. This further strengthens the high-K gate dielectric and improves the gate leakage current and interface state. Meanwhile, it reduces the thickness of the SiO₂ interface layer by making the high-K gate dielectric to react with the SiO₂ interface layer. 4) Strictly preventing invasion of oxygen during integration process. For example, after the metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure is etched, the metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure is protected by a Si₃N₄ spacer to avoid increasing of the EOT due to invasion of external oxygen atoms through side faces of the gate stack.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an HRTEM photograph of a HfLaON/SiO₂ interface layer/Si structure having an EOT of 0.62 nm and a SiO₂ interface layer thickness of 0.29 nm.

FIG. 2 shows a relationship between gate dielectric leakage current density and EOT of a TaN/HfLaON/SiO₂ interface layer structure, and a comparison with a poly-Si/SiO₂ gate structure. Under a same EOT, the gate dielectric leakage current of the TaN/HfLaON/SiO₂ interface layer structure is less than that of the poly-Si/SiO₂ gate structure by five orders.

It should be noted that the drawings are only for purpose of illustration and thus should not be construed as any limitation or constrain to the scope of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

The present disclosure provides a method for forming and controlling a molecular level SiO₂ interface layer for a CMOS device, the method mainly comprising:

Step 1) cleansing; after completing of local oxide isolation or shallow trench isolation in Gate-First process or removing replaced gate in Gate-Last process and before forming an interface oxide layer, cleansing a wafer and immersing the wafer in HF/isopropyl alcohol/water solution at room temperature, rinsing the wafer with deionized water, spinning the wafer and then putting the wafer into a furnace immediately, wherein a volume ratio of HF:isopropyl alcohol:water is 0.15-1.5%:0.01-0.10%:1%, and the wafer is immersed for 1-8 minutes; Step 2) forming the SiO₂ interface layer: performing rapid thermal annealing on the wafer optionally in super pure N₂ for 30-90 seconds at 500-600° C. in the Gate-Last process or at 600-800° C. in the Gate-First process, the SiO₂ interface layer having a thickness of 0.5-0.7 nm; Step 3) forming a high-K gate dielectric film: forming the high-K gate dielectric film by physical vapor deposition (PVD) or atom layer deposition (ALD), the high-K gate dielectric film having a thickness of 2-5 nm and comprising one of various high-K gate dielectric films, including a HfLaON film, a HfSiON film, and a HfSiAlON film (the high-K gate dielectric film is well known in the art and a detailed description thereof is omitted); Step 4) ultrasound cleansing: the product of the step 3) is subjected to ultrasound cleansing first with acetone for 5-10 minutes and then with absolute ethyl alcohol for 5-10 minutes and then is rinsed by deionized water and spun in N₂; Step 5) performing rapid thermal annealing: the rapid thermal annealing is conducted in super pure N₂ at 500-600° C. for 30-90 seconds in the Gate-Last process or at 800-1000° C. for 20-40 seconds in the Gate-First process; Step 6) forming the metal gate: depositing a metal nitride gate having a thickness of 3-40 nm on the high-K dielectric layer by reactive magnetic sputtering by PVD, wherein the metal nitride gate according to the present disclosure may be one of a TiN gate, a TaN gate, a MoN gate, a MoAlN gate, a TiAlN gate, and a TiGaN gate, which is well known in the art and thus a detailed description thereof is omitted; Step 7) depositing a barrier layer TaN or AlN on the metal gate by reactive magnetic sputtering, the barrier layer having a thickness of 4-6 nm; Step 8) on the barrier layer, depositing a polysilicon film having a thickness of 50-120 nm by low-pressure chemical vapor deposition (LPCVD) in the Gate-First process or depositing a low-resistance metal film having a thickness of 50-120 nm by magnetic sputtering in the gate-Last process, wherein the low-resistance metal according to the present disclosure may be commonly-used metal such as Mo, W, and TiAl, a detailed description thereof being omitted; Step 9) etching a product of the step 8) by plasma etching with Cl-base gas, F-base gas, or a mixture thereof, using a mask having a gate photolithography pattern, to form a polysilicon/metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure (the Gate-First process) or a metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure (the Gate-Last process), respectively; Step 10) depositing silicon nitride on a product of the step 9) by plasma chemical vapor deposition (PECVD) depositing at 300-400° C., the silicon nitride having a thickness of 200-600 Å; Step 11) etching the silicon nitride by anisotropic plasma etching to form silicon a nitride spacer-1; Step 12) for the Gate-First process, after source/drain extension implantation and forming a spacer-2, performing source/drain implantation to form source/drain regions; Step 13) for the Gate-First process, activating the source/drain regions by rapid thermal annealing: the rapid thermal annealing is performed at 950-1050° C. in N₂ for 1-15 seconds; and Step 14) forming contacts and metalizing: performing alloying annealing in N₂ or N₂+10% H₂ in an alloying furnace at 380-450° C. for 30-60 minutes.

The present disclosure can achieve the following advantageous effects:

1) The surface cleansing method according to the present disclosure can suppress generation of natural oxide and contamination of particles, and improve Interface micro-roughness. 2) Ultra-thin SiO₂ interface layer growth technology. The SiO₂ interface layer is grown utilizing a trace of oxygen contained in super pure N₂ during rapid thermal annealing. The technology has a good repeatability and is a key technology in achieving the good-quality high-K gate dielectric film having the small EOT. 3) Rapid thermal annealing in super pure N₂ further strengthens the high-K gate dielectric and improves the gate leakage current and interface state. Meanwhile, this reduces the thickness of the SiO₂ interface layer by making the high-K gate dielectric to react with the SiO₂ interface layer. 4) The metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure is protected by a Si₃N₄ spacer-1 to avoid increasing of the EOT due to invasion of external oxygen atoms through side faces of the gate stack.

The method for manufacturing and controlling the molecular level SiO₂ interface provided by the present disclosure can obtain a good-quality high-K gate dielectric film having a small EOT. The manufacturing process is simple and easy to integrate. It is compatible with planar CMOS process, and can satisfy requirement of high-performance nanometer level CMOS metal gate/high-K device of 45 nm and below. 

1. A method for forming and controlling a molecular level SiO₂ interface layer for a CMOS metal gate/high-K dielectric layer device, comprising: 1) cleansing: after completing local oxide isolation or shallow trench isolation in Gate-First process or removing replaced gate in Gate-Last process and before forming an interface oxide layer, cleansing a wafer and immersing the wafer in HF/isopropyl alcohol/water solution at room temperature, rinsing the wafer with deionized water, spinning the wafer and then putting the wafer into a furnace immediately, wherein a volume ratio of HF:isopropyl alcohol:water is 0.15-1.5%:0.01-0.10%:1%; 2) forming the SiO₂ interface layer: performing rapid thermal annealing on the wafer for 30-90 seconds in N₂ at 500-600° C. in the Gate-Last process or at 600-800° C. in the Gate-First process; 3) forming a high-K gate dielectric film: forming the high-K gate dielectric film by physical vapor deposition or atom layer deposition, the high-K gate dielectric film comprising one of various high-K gate dielectric films; 4) performing rapid thermal annealing: the rapid thermal annealing is conducted at 500-600° C. for 30-90 seconds in the Gate-Last process or at 800-1000° C. for 20-40 seconds in the Gate-First process; 5) forming the metal gate: depositing a metal nitride gate on the high-K dielectric layer by reactive magnetic sputtering utilizing physical vapor deposition; 6) depositing a barrier layer on the metal gate by reactive magnetic sputtering; 7) on the barrier layer, depositing polysilicon by low-pressure chemical vapor deposition in the Gate-First process or depositing low-resistance metal by magnetic sputtering in the gate-Last process; 8) etching a product of the step 7) by plasma etching with Cl-base gas, F-base gas, or a mixture thereof, using a mask having a gate photolithography pattern, to form a polysilicon/metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure or a metal gate/high-K dielectric layer/SiO₂ interface layer gate stack structure, respectively; 9) depositing silicon nitride on a product of the step 8) by plasma chemical vapor deposition at 300-400° C., the silicon nitride having a thickness of 200-600 Å; 10) etching the silicon nitride by anisotropic plasma etching to form silicon nitride a spacer-1; 11) after source/drain extension implantation and forming a spacer-2, performing source/drain implantation to form source/drain regions; 12) activating the source/drain regions by rapid thermal annealing: the rapid thermal annealing is performed at 950-1050° C. in N₂ for 1-15 seconds; and 13) forming contacts and metalizing: performing alloying annealing in N₂ or N₂+10% H₂ in an alloying furnace at 380-450° C.
 2. The method according to claim 1, wherein the cleansing in the step 1) is performed before formation of the interface oxide layer, wherein the wafer is first cleansed by a conventional method and then is immersed in the HF/isopropyl alcohol/water solution at the room temperature.
 3. The method according to claim 1, wherein in the step 2), the SiO₂ interface layer has a thickness of 0.5-0.7 nm.
 4. The method according to claim 1, wherein in the step 3), the high-K gate dielectric film has a thickness of 2-5 nm.
 5. The method according to claim 1, wherein in the step 3), the high-K gate dielectric film is one of a HfLaON film, a HfSiON film, and a HfSiAlON film.
 6. The method according to claim 1, wherein in the step 5), the metal nitride gate has a thickness of 3-40 nm.
 7. The method according to claim 1, wherein in the step 5), the metal nitride gate is one of a TiN gate, a TaN gate, a MoN gate, a MoAlN gate, a TiAlN gate, and a TiGaN gate.
 8. The method according to claim 1, wherein in the step 6), the barrier layer has a thickness of 4-7 nm.
 9. The method according to claim 1, wherein in the step 6), the barrier layer is a TaN layer or an AlN layer.
 10. The method according to claim 1, wherein in the step 7), the polysilicon film has a thickness of 50-120 nm, the low-resistance metal film has a thickness of 50-120 nm, and the low-resistance metal film is one of a Mo film, a W film, and a TiAl film.
 11. The method according to claim 4, wherein in the step 3), the high-K gate dielectric film is one of a HfLaON film, a HfSiON film, and a HfSiAlON film.
 12. The method according to claim 6, wherein in the step 5), the metal nitride gate is one of a TiN gate, a TaN gate, a MoN gate, a MoAlN gate, a TiAlN gate, and a TiGaN gate.
 13. The method according to claim 8, wherein in the step 6), the barrier layer is a TaN layer or an AlN layer. 